1. Field of the Invention
This invention relates to a transport belt such as can be used on machines for the production of web material for example, such as paper or paperboard for example. In particular, the present invention relates to a transport or process belt with variably adjustable release characteristics, and a method of manufacturing the transport or process belt.
2. Background and Related Information
Transport belts of this type are used in the production of paper, for example in regions in which the still wet paper material is passed through press sections in order to remove liquid still present in said material. For example, en route through two press rollers between the transport belt and the web material passes the still wet paper material, meaning the paper or the starting material for the paper, a thin liquid film from the water is pressed out of said material. Generally the transport belt is impermeable to water in order to provide as smooth a surface as possible and produce an accordingly unstructured image of this surface on the web material; hence the problem arises at the point where the transport belt is led away from web material that the existing thin film of liquid or water produces an adhesive effect. This impairs the releasing of the transport belt from the web material.
A method known from U.S. Pat. No. 6,962,885 B1, incorporated herein by reference in its entirety, to combat this problem is to provide, on the side of the transport belt which comes into contact with the web material, a thin layer which does not have a flat or smooth surface structure but a multiplicity of small depressions. The latter can be formed during the production of this thin layer by embedding grains of salt in the material. Where the gains of salt are not fully embedded they can be subsequently removed by dissolving in water, thus obtaining hollow spaces or depressions open to the surface. Water pressed out of the web material can be collected in these depressions and the adhesive effect can be at least lessened.
An approach known from EPO 576 115 B1, incorporated herein by reference in its entirety, is for the surface of the transport belt which comes into contact with the web material to be provided with a comparatively rough structure and at the same time to form this region of the transport belt from an elastic material. When the paper material is being pressed between two press rollers the comparatively rough surface is compressed. After it has passed through this press roller region the compressed transport belt relaxes, with the result that the serrated elevations forming the surface roughness create a disturbance in the existing water film, thus making it easier for the transport belt to detach from the web material.